In the operation of a tube and shell type heat exchanger in which a plurality of tubes of substantial length carry a first fluid in heat exchange relation to a second fluid surrounding the tubes, the development of a leak in the side wall of one of the tubes would necessitate the replacement of the heat exchanger unit or of the leaking tube, either of which is a time consuming and expensive procedure, unless the leaking tube is effectively closed off. To accomplish the closing off of a leaking tube, expandable plugs are placed at both ends of this tube, near its junctures with the heat exchanger headers. In order to keep the down time of the unit to a minimum, it is preferable that only one end of the unit be opened to expose the tube ends and the plugs for both ends of the leaking tube are inserted into the tube from the same end. There is difficulty in this procedure, however, that of locating and expanding the plug located at the remote end of the tube.
U.S. Pat. No. 2,764,184, Fitzhugh et al, discloses a plug designed to facilitate the placement and expansion of a plug at a remote location in the tube. The plug of Fitzhugh et al includes an expandable, cylindrical sleeve carried between first and second cylindrical body portions which have a threaded connection. The first body portion carries an eccentrically pivoted, triangular pawl serving to lock this portion against rotation while the second body portion includes a pair of T-shaped slots for engaging a cross pin of an actuating rod. The design of the Fitzhugh et al device, however, leaves the threaded interconnection between the two body portions exposed to the fluid which enters the plugged tube through the sidewall hole. As a result, the threads tend to become corroded, making the plug impossible to remove in a manner which would permit its subsequent reuse.
It is the primary object of the present invention to provide an expandable tube plug which may be inserted into and expanded from the remote end of a tube by the use of a simple socket wrench with suitable extensions and which provides a fluid tight seal not only between the plug and the inner wall of the tube but also around the threads interconnecting the portions of the plug to protect the threads from contamination or corrosion.
It is also an object of the invention to provide a tube plug which is characterized by its simplicity of construction and operation.